On 11.07.2014 [15:37:45 +0800], Jiang Liu wrote: > Current kernel only updates _mem_id_[cpu] for onlined CPUs when memory > configuration changes. So kernel may allocate memory from remote node > for a CPU if the CPU is still in absent or offline state even if the > node associated with the CPU has already been onlined. This just sounds like the topology information is being updated at the wrong place/time? That is, the memory is online, the CPU is being brought online, but isn't associated with any node? > This patch tries to improve performance by updating _mem_id_[cpu] for > each possible CPU when memory configuration changes, thus kernel could > always allocate from local node once the node is onlined. Ok, what is the impact? Do you actually see better performance? > We check node_online(cpu_to_node(cpu)) because: > 1) local_memory_node(nid) needs to access NODE_DATA(nid) > 2) try_offline_node(nid) just zeroes out NODE_DATA(nid) instead of free it > > Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx> > --- > mm/page_alloc.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 0ea758b898fd..de86e941ed57 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3844,13 +3844,13 @@ static int __build_all_zonelists(void *data) > /* > * We now know the "local memory node" for each node-- > * i.e., the node of the first zone in the generic zonelist. > - * Set up numa_mem percpu variable for on-line cpus. During > - * boot, only the boot cpu should be on-line; we'll init the > - * secondary cpus' numa_mem as they come on-line. During > - * node/memory hotplug, we'll fixup all on-line cpus. > + * Set up numa_mem percpu variable for all possible cpus > + * if associated node has been onlined. > */ > - if (cpu_online(cpu)) > + if (node_online(cpu_to_node(cpu))) > set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu))); > + else > + set_cpu_numa_mem(cpu, NUMA_NO_NODE); > #endif -- To unsubscribe from this list: send the line "unsubscribe linux-hotplug" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
